Who needs a photo under 40 KB?
40 KB sits between the common 20 KB and 50 KB limits: several state commission, university and scholarship portals cap the photo at 40 KB, and some ask for 20–40 KB.
Getting the best quality at 40 KB
Crop to head and shoulders on a plain light background before compressing. If the form gives a range such as 20–40 KB, aim for about 30 KB rather than right at the limit.
What size will the picture be?
About 800–950 pixels wide in JPG from a typical phone photo.
Questions
How do I compress a photo to 40 KB?
Drop it in: the size is already set to 40 KB. Press Compress and download; the result is always 40 KB or less.
My form says 20 KB to 40 KB
Keep 40 as the size and set 20 as the minimum under More options, so the file can't fall below it.
How do I make a JPG less than 40 KB?
Drop the photo in and press Compress: the size is already set, so the JPG always comes out under 40 KB. Phone photos and iPhone HEIC files work too, and you can do many at once.